What should be the minimum oxygen level inside a shelter when occupied?

• A. 20.9%
• B. 19.5%
• C. 16%
• D. 18%

Answer: (B)

Oxygen level safety for people inside a shelter is the main idea. Air normally has about 21% oxygen, but safety standards set 19.5% as the minimum acceptable concentration for occupied spaces. At or above 19.5%, most people can breathe normally and continue to function; once the level drops toward 18% or lower, symptoms of oxygen deprivation can appear and performance and judgment suffer. 16% is clearly dangerous. So the minimum safe level to maintain inside an occupied shelter is 19.5%. If it falls below that, increase ventilation or evacuate to ensure safety.